The present application claims foreign priority benefits under 35 U.S.C. xc2xa7119 for Patent Application Ser. No. 2000/2144 filed in the Republic of South Africa on May 3, 2000, and entitled xe2x80x9cLiquid Filter Using a Filtration Aid.xe2x80x9d
1. Technical Field
The present invention relates to fluid filtration systems. More particularly, the present invention relates to system and method for reducing the abrasive wear of filtration elements which comprises fluid filtration systems.
2. Description of the Related Art
Filters which employ a filter medium and a filtration aid, in order to avoid premature blinding of the filter medium and thereby to extend the cycle time between back washing procedures, generally operate on the principle that when the filter is turned off, the filter aid and dirt collected thereby fall to the bottom of the container. When the filter is started up again, inlet fluid serves to stir up the filtration aid from the bottom of the filter container so that the filter aid becomes coated onto the filter medium once more.
During this start-up process the filtration aid and dirt in the bottom of the container inflict wear on the filter medium which is generally a fabric bag or sleeve. The severity of the wear on the bag or sleeve depends largely on the direction and velocity of the flow of incoming liquid which stirs up the mixture of dirt and filtration aid. It has now been found that, depending on the exact configuration, an inlet arrangement wherein the flow of the incoming liquid directly impinges the filter medium can lead to undue wear on the bag or sleeve at least in the case of some filtration applications.
It is accordingly an object of this invention to provide an inlet arrangement which, whilst providing adequate dispersion of the settled mixture of filtration aid and dirt at start up, nevertheless diminishes the aforementioned abrasive effect on the filter medium fabric, particularly at the lower ends of bags or sleeves which are in the immediate vicinity of the settled dirt and filtration aid.
In accordance with this invention there is provided a liquid filter comprising a filter container having a generally cylindrical shape, an inlet through the side of the container towards the lower end thereof, an outlet from the container, and a filter medium or support for such filter medium interposed between the inlet and outlet and wherein the filter is adapted to utilize a filtration aid and to operate on the basis that at the termination of an operating cycle, the filtration aid and dirt associated therewith fall to the bottom of the container and the filtration aid and at least some dirt becomes stirred up and re-coated on the filter medium by liquid flowing into the container when the filter is started up once more, the liquid filter being characterized in that the inlet is fitted with a manifold having at least two outlet ports adapted to direct a portion of the inlet liquid in each in generally opposite or substantially divergent directions.
Further features of the invention provide for the manifold to comprise a radially extending inlet duct communicating with a transverse duct having at least two outlet ports directed in opposite or divergent directions; for the cross-sectional size of the inlet duct, the transverse duct, and the outlet ports to be substantially the same; and, if required, for each of the at least two outlet ports to be fitted with a cowl for directing inlet liquid somewhat downwards.
Additionally, the axis of each traverse duct and outlet port can be inclined somewhat downwards towards the bottom of the container but the two outlet ports are, nevertheless, directed in opposite or substantially divergent directions in plan view. In consequence of this arrangement, the velocity of inlet liquid and the force with which dirt and filtration aid carried by the liquid stream contact the bag or sleeve, is substantially diminished in consequence of which the wear on the lower ends of the fabric bags or sleeves is likewise substantially diminished.